Device for the determination of the resistance to friction



June 18, 1968 RIM. VAN 'DE VELDE 3,388,584

DEVICE FOR THE DETERMINATION OF THE RESISTANCE TO FRICTION Filed Oct. 27, 1965 INVENI'OR RENE M. VAN DE VELDE BY WATSON, COLE GRINDLE & WATSON ATTORNEYS United States Patent 3 388,584 DEVICE FOR THE llETERMINATION OF THE RESISTANCE T0 FRICTION Ren Marie Van de Velde, Edegem, Belgium, assignor to Gevaert-Agfa N.V., Mortsel, Belgium, a Belgian company Filed Oct. 27, 1965, Ser. No. 505,339 Claims priority, application Belgium, Nov. 4, 1964, 44,070, Patent 655,226 6 Claims. (Cl. 73-7) The present invention relates to a device for the determination of the resistance to friction of a strip of material. The invention is particularly intended for determining the resistance to friction of the backside of photographic paper webs, which are developed, fixed and rinsed in self-threading processing apparatus. In such self-threading processing apparatus the paper webs are usually advanced by means of driven roller pairs or by means of driven and non-driven rollers and a driven conveyor belt. These apparatus are designed so that the emulsion side of the photographic paper web does not contact driving parts in order to prevent the damaging of the light-sensitive gelatino-emulsion layer of the paper web, which layer has been softened in the processing baths. On the contrary, the backside of the paper web indeed contacts the driving parts and practice has shown that this backside can be damaged easily when its resistance to friction is insufficient. The damage at the backside of the paper web is caused by rubbing off a thin layer of paper fibres from said backside, usually in the direction opposite to the direction of the fibres of the material, whereby these rubbed off paper fibers are curled to form minuscule rolls and are floating in the liquid of the processing baths. These minuscule rolls settle down on the walls and the parts of the device or on the emulsion side of the treated paper web and may obstruct the feed lines for the liquid, the valves and the filters of the processing apparatus.

The object of the present invention is to provide a device for determining in a simple way the resistance to friction of a paper web.

Although the device according to the present invention is intended, in first place, to determine the resistance to friction of a photographic paper web which is to be treated in a self-threading treating apparatus, it is clear that the device according to the invention is as well suited for determining the resistance to friction of other materials besides photographic materials, which are submitted in a liquid to a mechanical transport or to a mechanical treatment in general. The application of the device according to the present invention is further not limited to the determination of the resistance to friction of materials to be treated in a liquid, but the said device may also find application in the determination of the resistance to friction of materials which are treated in dry state or, in general, in a defined medium or under defind circumstances.

Another object of the invention is to determine the direction of the fibres of a material.

The device according to the invention comprises a first member provided with a rubbing element, a second member provided with means to maintain a strip of material in a fixed position, and driving means to make both members execute a relative movement towards each other, during which the rubbing element cyclically exerts a rubbing action in the same sense and direction on the strip of material.

An exemplary embodiment of the invention will now be described with reference to the accompanying drawmg.

The device according to this embodiment is mounted "ice on a vertical plate 10 which is fitted to the bottom plate 11. On the shaft 12 driven by an electric motor, which is positioned behind the plate 10, a drum 13 is attached eccentrically. The drum cover has two oblique slits 14 and 15 for receiving the extremities of the strip of material 16 to be tested. For claritys sake the strip of material is drawn at a small distance from the drum cover. The front extremity of the strip of material is fixed tightly to the drum by means of a ratchet 17 which pushes this extremity in pressing relationship against the interior part of the drum cover. The ratchet 17 is pivotable about the pin 18 which is attached to the drum and this ratchet can be lifted by the operator in pushing on the arm 20 against the tension of the spring 19, said arm 20 being connected in a stationary way with the ratchet 17.

The arm 21 is provided above the drum and is pivotable about the pin 22 which is solidly attached to the plate 10. The arm 21 is pressed downwardly under the influence of gravity, and is retained by the screw 23 which is vertically adjustable in a square support 24, which is fitted on the plate 10.

A hook shaped element 25 bearing the rubbing element 26 is attached to the underside of the arm 21.

In the present embodiment the rubbing element was made out of a small strip of Para rubber (pure Brazilian rubber) the surface of which has been roughened by the impression of the textile belt which contacted the rubber strip in the course of its manufacture process. The rubber strip has a thickness of 3 mm. and a surfacial area of 8 cm. and was afiixed on the element 25 by sticking it thereto. The drum 13 is manufactured from stainless steel, it has a diameter of 10 cm., a width of 4 cm. and an eccentricity of 2 cm. The drum is rotated at a speed of 10 revolutions per minute. The rubbing element 26 presses on the drum surface with a power of 120 g. The device is further provided with a revolution counter 27 which is actuated by a cam on the drum (not illustrated in the drawing) and which permits to record the number of revolutions of the drum for a determined operation.

The device is operated as follows.

From the roll of material to be tested (in the present embodiment a roll of paper of g./m. intended for the preparation of photographic printing paper for use in automatic printing and processing apparatus) the operator separates a sheet which is then cut into a number of strips each measuring 220 x 25 mm. the longitudinal direction of the strips coinciding with the longitudinal direction of the web.

The strips to be tested in the device are first treated in developing, rinsing and fixing baths under the same circumstances in which the paper, to be used as a support for the preparation of the photographic printing paper, will be treated in the printing apparatus after exposure.

Thereupon one strip is attached to the drum cover surface 13. To this end the arm 21 is lifted up, the ratchet 17 is pressed away and one extremity of the strip of paper 16 is introduced into the slit 15 and tightly fixed therein, then the other extremity of said strip is passed through the slit 14 and finally the arm 21 is returned to its original horizontal position. The counter is set at zero and the motor driving the drum is started. The drum rotates in the direction indicated by the arrow and at each revolution the rubbing element 26 contacts a part of the strip of paper between the slits 15 and 14 whereby the arm 21 is lifted up and thus exerts a constant pressure on this strip material. After a defined number of revolutions the device is stopped, the strip of paper is removed from the drum and replaced by a second strip of paper which is attached on the drum in such a way that the direction of the fibres thereof is opposite to the direction of the fibres of the first strip. This second strip of paper is submitted to a number of rubbing actions which is identical to the number of rubbing actions performed on the first strip, whereupon this second strip is removed from the drum surface. The comparison between both strips immediately reveals that one strip has been damaged to a considerably greater extent than the other strip, because the sense of rubbing with one strip, through the device, was opposite to the direction of the fibres at its surface.

The friction tests on the following strips of paper are all carried out in the direction which is opposite to the direction of the fibres of the strips since, in this direction the strip of paper is more subject to damage during its displacement through the processing apparatus.

Another number of strips of paper are then submitted to rubbing movements in the device according to the present invention. For each strip the operator checks and notices how many rubbing movements were carried out before the fibres become detached. He determines the average number of the recorded rubbing movements and compares this number with the number of rubbing movements known from foregoing tests for a material which possesses a sufficient resistance to friction. If the thus found number is inferior than the known number, it is to be expected that the material will be damaged in selfthreading processing apparatus.

When using the described device the operator must pay attention thereto that the surface of the rubbing element does not undergo any serious changes, such as e.g. the wearing of the surface of the rubbing element, the covering of this surface with minuscule fibres detached from the strip of paper or with products having served for treating the strip of paper or its surface, etc. By regularly cleaning and/or washing the surface of the rubbing element and replacing the rubbing element in time when wearing is noticed, a very efiicient operation of the device is obtained. It is always possible to check the state of the rubbing element by determining the resistance to friction of a known strip of material and by comparing the resulted number with the number found by means of a new rubbing element for the concerned strip of material.

It is clear that the device according to the invention is also suited for determining the resistance to friction of other kinds of papers than photographic paper materials.

Further the friction test can also be executed on strips of paper which have not previously been moistened or immersed.

Finally other materials besides paper, such as webs of textiles, webs of synthetic materials, webs provided with a vacuum-deposited layer, etc., can be submitted to the friction test in the device according to the present invention.

The device may also comprise means for changing the pressure exerted by the rubbing element on the test strip 16, said means consisting e.-g. of small weights which can be attached to the arm 21.

Finally, the device according to the present invention may be operated at higher speeds than mentioned hereinbefore, so that e.g. the member bearing the test strip makes a multiple of ten movements per minute and even more. Under these circumstances a visual check by the operator during the operation of the device becomes impossible. According to a modified embodiment the device may comprise means which makes the device execute a defined number of rubbing movements whereupon it stops. The operator checks whether the test strip has been damaged and in case no damage was noticed, he restarts the device to make an identical number of rubbing movements. According to a further modified embodiment the device can perform cyclically a number of accelerated rubbing movements and one or some slackened rubbing movements. The operator will interrupt the operation of the device when he notices a damaging of the test strip during the performance of the slackcned rubbing movement(s).

What I claim is:

1. Device for determining the resistance to friction of a strip of test material, which comprises a support for said strip having an arcuate peripheral surface portion on which said strip is mounted, means for rotating said support about an axis of rotation having an eccentric relation with the curvature of said arcuate surface portion, the length of the radii of said surface at the ends of said strip being less than the radius of said surface intermediate said strip ends, a friction element for cyclically contacting said test strip as the same revolves with said strip support, a friction element support movable towards and away from said rotation axis, said element support being biased toward said axis, and stop means for limiting the movement of said element support towards said axis to maintain a clearance therebetween in excess of the radii of said strip supporting surface at said strip ends.

2. The device of claim 1 wherein said friction element has a generally planar surface extending substantially parallel to said rotation axis.

3. The device according to claim 1 wherein said strip support is a drum arranged eccentrically on a rotatably supported shaft.

4. The device of claim 1 wherein said stop means is adjustable to vary the length of said strip contacted by said friction element.

5. The device of claim 1 wherein said element support is a lever mounted at one end of a pivot axis arranged in spaced parallel relation to said rotational axis, said lever being engaged adjacent its other end by said stop means and carrying said friction element intermediate said ends.

'6. The device of claim 5 wherein said lever is positioned above said strip support and is biased by gravity.

References Cited UNITED STATES PATENTS 1,850,056 3/1932 Abbott 73-7 2,292,577 8/1942 Mahannah 737 2,561,133 7/1951 Petlcewicz 73-7 2,687,641 8/1954 Stout 73-7 LOUIS R. PRINCE, Primary Examiner.

JERRY NOLTON, Assistant Examiner. 

1. DEVICE FOR DETERMINING THE RESISTANCE TO FRICTION OF A STRIP OF TEST MATERIAL, WHICH COMPRISES A SUPPORT FOR SAID STRIP HAVING AN ARCUATE PERIPHERAL SURFACE PORTION ON WHICH SAID STRIP IS MOUNTED, MEANS FOR ROTATING SAID SUPPORT ABOUT AN AXIS OF ROTATION HAVING AN ECCENTRIC RELATION WITH THE CURVATURE OF SAID ARCUATE SURFACE PORTION, THE LENGTH OF THE RADII OF SAID SURFACE AT THE ENDS OF SAID STRIP BEING LESS THAN THE RADIUS OF SAID SURFACE INTERMEDIATE SAID STRIP ENDS, A FRICTION ELEMENT FOR CYCLICALLY CONTACT ING SAID TEST STRIP AS THE SAME REVOLVES WITH SAID STRIP SUPPORT, A FRICTION ELEMENT SUPPORT MOVABLE TOWARDS AND AWAY FROM SAID ROTATION AXIS, SAID ELEMENT SUPPORT BEING BIASED TOWARD SAID AXIS, AND STOP MEANS FOR LIMITING THE MOVEMENT OF SAID ELEMENT SUPPORT TOWARDS SAID AXIS TO MAINTAIN A CLEARANCE THEREBETWEEN IN EXCESS OF THE RADII OF SAID STRIP SUPPORTING SURFACE AT STRIP ENDS. 